Chemically strengthenable lithium aluminosilicate glasses with inherent damage resistance

ABSTRACT

A group of glass compositions in the Li 2 O—Al 2 O 3 —SiO 2 —B 2 O 3  family that can be chemically strengthened in single or multiple ion exchange baths containing at least one of NaNO 3  and KNO 3  for a short time (2-4 hours) to develop a deep depth of layer (DOL). In some instances, the DOL is at least 70 μm; in others, at least about 100 μm. The ion exchanged glasses have a high damage resistance (indentation fracture toughness ranging form greater than 10 kgf to greater than 50 kgf) that is better than or at least comparable to that of sodium aluminosilicate glasses.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claim is a continuation of U.S. application Ser. No.16/193,266, filed Nov. 16, 2018, which is a divisional of U.S.application Ser. No. 15/400,267, filed Jan. 6, 2017, which claims thebenefit of priority under 35 U.S.C. § 119 of U.S. ProvisionalApplication Ser. No. 62/276,431, filed Jan. 8, 2016, the contents ofeach of which are relied upon and incorporated herein by reference intheir entirety.

BACKGROUND

The disclosure relates to ion exchangeable glasses. More particularly,the disclosure relates to ion exchangeable lithium aluminosilicateglasses. Even more particularly, the disclosure relates to lithiumaluminosilicate glasses which, when ion exchanged, have high levels ofinherent damage resistance.

There have been continuous efforts in the development of new glasscompositions to improve ion exchange properties and higher damageresistance while facilitating melting and forming processes. Manyglasses with high indentation threshold are based on theSiO₂—Al₂O₃—B₂O₃—MgO—Na₂O—P₂O₅ glass systems. The open structure (i.e.high molar volume) resulting from the existence of boron or phosphorusleads to high inherent damage resistance (IDR).

SUMMARY

A group of glass compositions in the Li₂O—Al₂O₃—SiO₂—B₂O₃ family isprovided. These glasses can be chemically strengthened in single ormultiple ion exchange baths containing at least one of NaNO₃ and KNO₃for a short time (2-4 hours) to develop a deep depth of layer (DOL). Insome instances, the DOL is at least 70 μm; in others, at least about 100μm. The ion exchanged glasses have a high damage resistance (indentationfracture toughness ranging from greater than 10 kgf to greater than 50kgf) that is better than or at least comparable to that of sodiumaluminosilicate glasses.

Accordingly, one aspect of the disclosure is to provide a lithiumaluminosilicate glass. The glass comprises: from about 55 mol % to about75 mol % SiO₂; from about 9 mol % to about 18 mol % Al₂O₃; from about2.5 mol % to about 20 mol % B₂O₃; from about 3 mol % to about 20 mol %Li₂O; and from 0 mol % to about 4 mol % P₂O₅.

Another aspect of the disclosure is to provide a lithium aluminosilicateglass. The glass is ion exchanged and has a compressive layer extendingto a depth of layer of at least about 70 μm from at least one surfaceinto the glass. The compressive layer having a maximum compressivestress at the surface of at least about 600 MPa. The glass also has aVickers crack initiation threshold of at least about 10 kgf and a Knoopscratch threshold of at least about 8 N.

According to a first aspect of the disclosure a lithium aluminosilicateglass is provided. The lithium aluminosilicate glass comprises: fromabout 55 mol % to about 75 mol % SiO₂; from about 10 mol % to about 18mol % Al₂O₃; from about 3.5 mol % to about 9.5 mol % B₂O₃; from about 7mol % to about 14 mol % Li₂O; and from 0 mol % to about 4 mol % P₂O₅,wherein Li₂O (mol %)/R₂O (mol %) is in a range from about 0.1 to about0.4 and R₂O=Li₂O+Na₂O+K₂O+Rb₂O+Cs₂O.

According to a second aspect of the disclosure, the lithiumaluminosilicate glass of the first aspect is ion exchanged.

According to a third aspect of the disclosure, the ion exchanged lithiumaluminosilicate glass of the second aspect has a compressive layerextending to a depth of layer of at least about 70 μm from at least onesurface into the glass, the compressive layer having a maximumcompressive stress of at least about 600 MPa.

According to a fourth aspect of the disclosure, in the ion exchangedlithium aluminosilicate glass of the third aspect the compressive layerhas a compressive stress of at least about 100 MPa at a depth of 50 μmbelow the surface.

According to a fifth aspect of the disclosure, the ion exchanged lithiumaluminosilicate glass of any of the second through fourth aspects has aVickers crack initiation threshold of at least about 10 kgf.

According to a sixth aspect of the disclosure, the ion exchanged lithiumaluminosilicate glass of any of the second through fifth aspects has aKnoop scratch threshold of at least about 8 N.

According to a seventh aspect of the disclosure, the lithiumaluminosilicate glass of any of the first through sixth aspects has aliquidus viscosity of at least about 10 kP.

According to an eighth aspect of the disclosure, the lithiumaluminosilicate glass of any of the first through seventh aspects has asoftening point of about 840° C. or less.

According to a ninth aspect of the disclosure, the lithiumaluminosilicate glass of any of the first through eighth aspects has ananneal point of at least about 510° C.

According to a tenth aspect of the disclosure, the lithiumaluminosilicate glass of any of the first through ninth aspects has anelastic modulus of at least about 68 GPa.

According to an eleventh aspect of the disclosure, the lithiumaluminosilicate glass of any of the first through tenth aspects isprovided wherein R₂O (mol %) −Al₂O₃ (mol %) is in a range from about −2mol % to about 5.6 mol %.

According to a twelfth aspect of the disclosure, the lithiumaluminosilicate glass of any of the first through eleventh aspects isprovided wherein Al₂O₃ (mol %)>B₂O₃ (mol %).

According to a thirteenth aspect of the disclosure, the lithiumaluminosilicate glass of any of the first through twelfth aspects isprovided wherein the lithium aluminosilicate glass comprises: from about58 mol % to about 69 mol % SiO₂; from about 10 mol % to about 17 mol %Al₂O₃; from about 3.5 mol % to about 9.5 mol % B₂O₃; from 0 mol % toabout 2.5 mol % P₂O₅; from about 7 mol % to about 14 mol % Li₂O; fromabout 0.2 mol % to about 14 mol % Na₂O; from 0 mol % to about 2.5 mol %K₂O; from 0 mol % to about 5 mol % MgO; and from 0 mol % to about 4 mol% ZnO, wherein Li₂O (mol %)/R₂O (mol %) is in a range from about 0.1 toabout 0.4.

According to a fourteenth aspect of the disclosure, the lithiumaluminosilicate glass of any of the first through thirteenth aspects isprovided wherein the lithium aluminosilicate glass comprises: from about5 mol % to about 9 mol % B₂O₃; from about 7 mol % to about 10 mol %Li₂O; from about 4 mol % to about 14 mol % Na₂O; and from 0 mol % toabout 1 mol % K₂O.

According to a fifteenth aspect of the disclosure, the lithiumaluminosilicate glass of any of the first through fourteenth aspects isprovided wherein (Al₂O₃ (mol %)+B₂O₃ (mol %))/R₂O (mol %) is in a rangefrom about 0.9 to about 1.9.

According to a sixteenth aspect of the disclosure, the lithiumaluminosilicate glass of any of the first through fifteenth aspects isprovided wherein R₂O (mol %)+R′O (mol %) −Al₂O₃ (mol %) −B₂O₃ (mol %)−P₂O₅ (mol %) is in a range from about −10.5 mol % to about −0.11 mol %,where R′O=MgO+CaO+SrO+BaO.

According to a seventeenth aspect of the disclosure, the lithiumaluminosilicate glass of any of the first through sixteenth aspects isprovided wherein the lithium aluminosilicate glass comprises from about5 mol % to about 12 mol % Li₂O.

According to an eighteenth aspect of the disclosure, the lithiumaluminosilicate glass of any of the first through seventeenth aspects isprovided wherein the lithium aluminosilicate glass comprises: from 0 mol% to about 5 mol % Na₂O; from 0 mol % to about 4 mol % K₂O; from 0 mol %to about 8 mol % MgO; from 0 mol % to about 4 mol % ZnO; from 0 mol % toabout 5 mol % TiO₂; and from 0 mol % to about 3 mol % P₂O₅.

According to a nineteenth aspect of the disclosure, the lithiumaluminosilicate glass of any of the first through eighteenth aspects isprovided wherein the lithium aluminosilicate glass comprises: from about55 mol % to about 60 mol % SiO₂; from about 12 mol % to about 15 mol %Al₂O₃; from about 3.5 mol % to about 7.5 mol % B₂O₃; from about 7 mol %to about 10 mol % Li₂O; and from 0 mol % to about 3 mol % P₂O₅.

According to a twentieth aspect of the disclosure, the lithiumaluminosilicate glass of any of the first through nineteenth aspects isprovided wherein the lithium aluminosilicate glass comprises from about5 mol % to about 7 mol % B₂O₃.

According to a twenty-first aspect of the disclosure, the lithiumaluminosilicate glass of any of the first through twentieth aspects isprovided wherein the lithium aluminosilicate glass comprises: from 0 mol% to about 5 mol % Na₂O; and from about 0.05 mol % to about 0.5 mol %SnO₂.

According to a twenty-second aspect of the disclosure a consumerelectronic product is provided. The consumer electronic productcomprises: a housing having a front surface, a back surface and sidesurfaces; electrical components provided at least partially within thehousing, the electrical components including at least a controller, amemory, and a display, the display being provided at or adjacent thefront surface of the housing; and a cover glass disposed over thedisplay, wherein at least one of a portion of the housing or the coverglass comprises the lithium aluminosilicate glass of any of the firstthrough twenty-first aspects.

According to a twenty-third aspect of the disclosure a consumerelectronic product is provided. The lithium aluminosilicate glasscomprises: from about 55 mol % to about 75 mol % SiO₂; from about 10 mol% to about 18 mol % Al₂O₃; from about 2.5 mol % to about 7.5 mol % B₂O₃;from about 5 mol % to about 14 mol % Li₂O; from 0 mol % to about 4 mol %P₂O₅; and from 0 mol % to about 1 mol % K₂O; wherein Li₂O (mol %)/R₂O(mol %) is in a range from about 0.1 to about 0.4,R₂O=Li₂O+Na₂O+K₂O+Rb₂O+Cs₂O, R₂O (mol %)+R′O (mol %) −Al₂O₃ (mol %)−B₂O₃ (mol %)−P₂O₅ (mol %) is in a range from about −10.5 mol % to about−0.11 mol %, and R′O=MgO+CaO+SrO+BaO.

According to a twenty-fourth aspect of the disclosure, the lithiumaluminosilicate glass of the twenty-third aspect is ion exchanged.

According to a twenty-fifth aspect of the disclosure, the ion exchangedlithium aluminosilicate glass of the twenty-fourth aspect has acompressive layer extending to a depth of layer of at least about 70 μmfrom at least one surface into the glass, the compressive layer having amaximum compressive stress of at least about 600 MPa.

According to a twenty-sixth aspect of the disclosure, in the ionexchanged lithium aluminosilicate glass of the twenty-fifth aspect thecompressive layer has a compressive stress of at least about 100 MPa ata depth of 50 μm below the surface.

According to a twenty-seventh aspect of the disclosure, the lithiumaluminosilicate glass of any of the twenty-third through twenty-sixthaspects has a Vickers crack initiation threshold of at least about 10kgf.

According to a twenty-eighth aspect of the disclosure, the lithiumaluminosilicate glass of any of the twenty-third through twenty-seventhaspects has a Knoop scratch threshold of at least about 8 N.

According to a twenty-ninth aspect of the disclosure, the lithiumaluminosilicate glass of any of the twenty-third through twenty-eighthaspects has a liquidus viscosity of at least about 10 kP.

According to a thirtieth aspect of the disclosure, the lithiumaluminosilicate glass of any of the twenty-third through twenty-ninthaspects has a softening point of about 840° C. or less.

According to a thirty-first aspect of the disclosure, the lithiumaluminosilicate glass of any of the twenty-third through thirtiethaspects has an anneal point of at least about 510° C.

According to a thirty-second aspect of the disclosure, the lithiumaluminosilicate glass of any of the twenty-third through thirty-firstaspects has an elastic modulus of at least about 68 GPa.

According to a thirty-third aspect of the disclosure, the lithiumaluminosilicate glass of any of the twenty-third through thirty-secondaspects is provided wherein R₂O (mol %)−Al₂O₃ (mol %) is in a range fromabout −2 mol % to about 5.6 mol %.

According to a thirty-fourth aspect of the disclosure, the lithiumaluminosilicate glass of any of the twenty-third through thirty-thirdaspects is provided wherein Al₂O₃ (mol %)>B₂O₃ (mol %).

According to a thirty-fifth aspect of the disclosure, the lithiumaluminosilicate glass of any of the twenty-third through thirty-fourthaspects is provided wherein (Al₂O₃ (mol %)+B₂O₃ (mol %))/R₂O (mol %) isin a range from about 0.9 to about 1.9.

According to a thirty-sixth aspect of the disclosure, the lithiumaluminosilicate glass of any of the twenty-third through thirty-fifthaspects is provided wherein the lithium aluminosilicate glass comprises:from 0 mol % to about 5 mol % Na₂O; from 0 mol % to about 8 mol % MgO;from 0 mol % to about 4 mol % ZnO; from 0 mol % to about 5 mol % TiO₂;and from 0 mol % to about 3 mol % P₂O₅.

According to a thirty-seventh aspect of the disclosure, the lithiumaluminosilicate glass of any of the twenty-third through thirty-sixthaspects is provided wherein the lithium aluminosilicate glass comprisesfrom about 5 mol % to about 7 mol % B₂O₃.

According to a thirty-eighth aspect of the disclosure, the lithiumaluminosilicate glass of any of the twenty-third through thirty-seventhaspects is provided wherein the lithium aluminosilicate glass comprises:from 0 mol % to about 5 mol % Na₂O; and from about 0.05 mol % to about0.5 mol % SnO₂.

According to a thirty-ninth aspect of the disclosure a consumerelectronic product is provided. The consumer electronic productcomprises: a housing having a front surface, a back surface and sidesurfaces; electrical components provided at least partially within thehousing, the electrical components including at least a controller, amemory, and a display, the display being provided at or adjacent thefront surface of the housing; and a cover glass disposed over thedisplay, wherein at least one of a portion of the housing or the coverglass comprises the lithium aluminosilicate glass of any of thetwenty-third through thirty-eighth aspects.

According to a fortieth aspect of the disclosure a lithiumaluminosilicate glass is provided. The lithium aluminosilicate glass ision exchanged and has a compressive layer extending to a depth of layerof at least about 70 μm from at least one surface into the glass, thecompressive layer having a maximum compressive stress of at least about600 MPa, wherein the glass has a Vickers crack initiation threshold ofat least about 10 kgf and a Knoop scratch threshold of at least about 8N.

According to a forty-first aspect of the disclosure a consumerelectronic product is provided. The consumer electronic productcomprises: a housing having a front surface, a back surface and sidesurfaces; electrical components provided at least partially within thehousing, the electrical components including at least a controller, amemory, and a display, the display being provided at or adjacent thefront surface of the housing; and a cover glass disposed over thedisplay, wherein at least one of a portion of the housing or the coverglass comprises the lithium aluminosilicate glass of the fortiethaspect.

These and other aspects, advantages, and salient features of the presentdisclosure will become apparent from the following detailed description,the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional schematic view of an ion exchanged glassarticle;

FIG. 2 is a plot of Na⁺ concentration profile from the surface of theglass to the inner portion of the glass for a lithium aluminosilicateglass of the present disclosure (A) and a glass ceramic (B);

FIG. 3 is a plot of indentation fracture threshold for a lithiumaluminosilicate glass of the present disclosure, ion exchanged at 390°C. in NaNO₃ for 3.5 hours, and sodium aluminosilicate glasses after ionexchange in KNO₃;

FIG. 4 shows optical microscopic images of Vickers indentations in theion exchanged lithium aluminosilicate glass plotted in FIG. 3 underindenter loads of 10 kgf, 30 kgf, and 50 kgf;

FIG. 5A is a plan view of an exemplary electronic device incorporatingany of the articles disclosed herein; and

FIG. 5B is a perspective view of the exemplary electronic device of FIG.5A.

DETAILED DESCRIPTION

In the following description, like reference characters designate likeor corresponding parts throughout the several views shown in thefigures. It is also understood that, unless otherwise specified, termssuch as “top,” “bottom,” “outward,” “inward,” and the like are words ofconvenience and are not to be construed as limiting terms. In addition,whenever a group is described as comprising at least one of a group ofelements and combinations thereof, it is understood that the group maycomprise, consist essentially of, or consist of any number of thoseelements recited, either individually or in combination with each other.Similarly, whenever a group is described as consisting of at least oneof a group of elements or combinations thereof, it is understood thatthe group may consist of any number of those elements recited, eitherindividually or in combination with each other. Unless otherwisespecified, a range of values, when recited, includes both the upper andlower limits of the range as well as any ranges therebetween. As usedherein, the indefinite articles “a,” “an,” and the correspondingdefinite article “the” mean “at least one” or “one or more,” unlessotherwise specified. It also is understood that the various featuresdisclosed in the specification and the drawings can be used in any andall combinations.

As used herein, the terms “glass article” and “glass articles” are usedin their broadest sense to include any object made wholly or partly ofglass. Unless otherwise specified, all compositions are expressed interms of mole percent (mol %). Coefficients of thermal expansion (CTE)are expressed in terms of 10⁻⁷/° C. and represent a value measured overa temperature range from about 20° C. to about 300° C., unless otherwisespecified.

Unless otherwise specified, all temperatures are expressed in terms ofdegrees Celsius (° C.). As used herein the term “softening point” refersto the temperature at which the viscosity of a glass is approximately10^(7.6) poise (P), the term “anneal point” refers to the temperature atwhich the viscosity of a glass is approximately 10¹³² poise, the term“200 poise temperature (T^(200P))” refers to the temperature at whichthe viscosity of a glass is approximately 200 poise, the term “1 poisetemperature (T^(200P))” refers to the temperature at which the viscosityof a glass is approximately 200 poise, the term “10¹¹ poise temperature”refers to the temperature at which the viscosity of a glass isapproximately 10¹¹ poise, the term “35 kP temperature (T^(35P))” refersto the temperature at which the viscosity of a glass is approximately 35kilopoise (kP), and the term “160 kP temperature (T^(160kP))” refers tothe temperature at which the viscosity of a glass is approximately 160kP. As used herein, the term “liquidus temperature,” or “T^(L)” refersto the temperature at which crystals first appear as a molten glasscools down from the melting temperature, or the temperature at which thevery last crystals melt away as temperature is increased from roomtemperature.

It is noted that the terms “substantially” and “about” may be utilizedherein to represent the inherent degree of uncertainty that may beattributed to any quantitative comparison, value, measurement, or otherrepresentation. These terms are also utilized herein to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter at issue. Thus, a glass that is “substantially free ofMgO” is one in which MgO is not actively added or batched into theglass, but may be present in very small amounts (e.g., less than 0.1 mol%) as a contaminant.

Referring to the drawings in general and to FIG. 1 in particular, itwill be understood that the illustrations are for the purpose ofdescribing particular embodiments and are not intended to limit thedisclosure or appended claims thereto. The drawings are not necessarilyto scale, and certain features and certain views of the drawings may beshown exaggerated in scale or in schematic in the interest of clarityand conciseness.

Described herein are ion exchangeable lithium aluminosilicate glassesthat exhibit high levels of damage resistance—also referred to as nativedamage resistance or inherent damage resistance—as characterized byVickers crack initiation threshold and Knoop scratch testing, whenchemically strengthened. These glasses may in general be ion exchangedin sodium salts (e.g., NaNO₃) at faster rates than analogous sodiumalkali aluminosilicate glasses are ion exchanged in potassium salts(e.g., KNO₃). Deeper depths of compression (also referred to as “depthof layer” or “DOL”) may also be achieved at lower temperatures with thelithium-containing glasses. When Na+ replaces Li+ in the glass, the rateof diffusion may be about 10 times faster than exchange of K⁺ for Na⁺ inthe glass. Mixed salt baths may be used to allow for dual ion exchangein which both K⁺ for Na⁺ and Na⁺ for Li⁺ exchange occur, resulting in adeep depth of compression due to the Na⁺ for Li⁺ exchange and highsurface compressive stress due to the K⁺ for Na⁺ exchange.

The lithium aluminosilicate glasses described herein comprise or consistessentially of: from about 55 mol % to about 75 mol % SiO₂ (55 mol%≤SiO₂≤75 mol %); from about 9 mol % to about 18 mol % Al₂O₃ (9 mol%≤Al₂O₃≤18 mol %); from about 2.5 mol % to about 20 mol % B₂O₃ (2.5 mol%≤B₂O₃≤20 mol %); from about 3 mol % to about 20 mol % Li₂O (3 mol%≤Li₂O≤20 mol %); and from 0 mol % to about 4 mol % P₂O₅ (0 mol %≤P₂O₅≤4mol %). In some embodiments, the glass further comprises at least oneof: from 0 mol % to about 5 mol % Na₂O; from 0 mol % to about 4 mol %K₂O; from 0 mol % to about 8 mol % MgO; from 0 mol % to about 4 mol %ZnO, and from 0 mol % to about 5 mol % TiO₂.

In particular embodiments, the lithium aluminosilicate glasses describedherein comprise or consist essentially of: from about 55 mol % to about75 mol % SiO₂; from about 10 mol % to about 18 mol % Al₂O₃; from 0 mol %to about 20 mol % B₂O₃; from about 5 mol % to about 14 mol % Li₂O; from0 mol % to about 5 mol % Na₂O; from 0 mol % to about 4 mol % K₂O; from 0mol % to about 8 mol % MgO; from 0 mol % to about 4 mol % ZnO; from 0mol % to about 5 mol % TiO₂; from 0 mol % to about 4 mol % P₂O₅, andfrom about 0.05 mol % to about 0.5 mol % SnO₂. Even more particularly,the glass may comprise or consist essentially of: from about 55 mol % toabout 60 mol % SiO₂ (55 mol %≤SiO₂≤60 mol %); from about 12 mol % toabout 15 mol % Al₂O₃ (12 mol %≤Al₂O₃≤15 mol %); from about 2.5 mol % toabout 7.5 mol % B₂O₃ (2.5 mol %≤B₂O₃≤7.5 mol %); from about 7 mol % toabout 10 mol % Li₂O (7 mol %≤Li₂O≤10 mol %); and from 0 mol % to about 3mol % P₂O₅ (0 mol %≤P₂O₅≤3 mol %). Most preferably, B₂O₃ is in a rangefrom about 5 mol % to about 7 mol %. Non-limiting examples of thecompositions of such glasses and a reference composition (9667) arelisted in Table 1.

TABLE 1 Examples of the lithium aluminosilicate glasses. mol % Reference1 2 3 4 5 oxide 9667 REN REO RET RGC RDD SiO₂ 69.2 65.0 63.0 59.3 63.367.3 Al₂O₃ 12.6 14.4 15.5 15.4 15.3 13.5 B₂O₃ 1.8 2.3 2.3 6.0 6.0 2.0Li₂O 7.7 8.8 9.7 9.7 9.6 7.7 Na₂O 0.4 0.6 0.6 0.6 0.6 0.6 MgO 2.9 4.04.0 4.0 4.0 4.0 ZnO 1.7 1.2 1.2 1.2 1.2 1.2 TiO₂ 3.5 3.5 3.5 3.6 0.0 3.5SnO₂ 0.2 0.2 0.2 0.2 0.2 0.2 P₂O₅ 0 0 0 0 0 0 mol % 6 7 8 9 10 11 oxideRDE RDF RDG RDH RDI RFX SiO₂ 65.9 64.7 63.4 62.3 61.0 68.9 Al₂O₃ 13.213.0 12.7 12.5 12.2 13.9 B₂O₃ 4.0 5.8 7.6 9.2 10.9 2.4 Li₂O 7.5 7.5 7.37.1 7.1 7.9 Na₂O 0.6 0.6 0.6 0.6 0.5 0.6 MgO 4.0 3.8 3.8 3.7 3.7 4.1 ZnO1.2 1.1 1.1 1.1 1.1 1.2 TiO₂ 3.4 3.4 3.3 3.3 3.2 0 SnO₂ 0.2 0.2 0.2 0.20.2 0.1 P₂O₅ 0 0 0 0 0 0.9 mol % 12 13 14 15 oxide RFY RFZ RGA RGB SiO₂68.2 67.6 66.9 69.5 Al₂O₃ 13.8 13.6 13.5 14.0 B₂O₃ 2.3 2.3 2.3 2.4 Li₂O7.9 7.8 7.7 8.0 Na₂O 0.6 0.6 1.7 0.6 MgO 4.0 4.0 4.0 4.1 ZnO 1.2 1.2 1.21.2 TiO₂ 0 0 0 0 SnO₂ 0.1 0.1 0.1 0.1 P₂O₅ 1.8 2.7 2.7 0.0

In particular embodiments, the lithium aluminosilicate glasses describedherein comprise or consist essentially of: from about 58 mol % to about69 mol % SiO₂ (58 mol %≤SiO₂≤69 mol %); from about 9 mol % to about 17mol % Al₂O₃ (9 mol %≤Al₂O₃≤17 mol %); from about 3.5 mol % to about 9.5mol % B₂O₃ (3.5 mol %≤B₂O₃≤9.5 mol %); from 0 mol % to about 2.5 mol %P₂O₅ (0 mol %≤P₂O₅≤4 mol %); from about 2.5 mol % to about 12 mol % Li₂O(2.5 mol %≤Li₂O≤12 mol %); from about 0.2 mol % to about 12 mol % Na₂O(0.2 mol %≤Na₂O≤13 mol %); from 0 mol % to about 2.5 mol % K₂O (0 mol%≤K₂O≤2.5 mol %); 0 mol % to about 5 mol % MgO (0 mol %≤MgO≤5 mol %);and/or from 0 mol % to about 4 mol % ZnO (0 mol %≤ZnO≤4 mol %). Moreparticularly, the glass may comprise: from about 5 mol % to about 9 mol% B₂O₃ (5 mol %≤B₂O₃≤9 mol %); from about 4 mol % to about 10 mol % Li₂O(4 mol %≤Li₂O≤10 mol %); from about 4 mol % to about 14 mol % Na₂O (4mol %≤Na₂O≤14 mol %); from 0 mol % to about 1 mol % K₂O (0 mol %≤K₂O≤1mol %); 0 mol % to about 3 mol % MgO (0 mol %≤MgO≤3 mol %); and/or from0 mol % to about 3 mol % ZnO (0 mol %≤ZnO≤3 mol %). These glasses mayfurther include from about 0.05 mol % to about 0.5 mol % SnO₂ (0.05 mol%≤SnO₂≤0.5 mol %). Non-limiting examples of the compositions of suchglasses are listed in Table 2.

In some embodiments, (Li₂O (mol %)/R₂O (mol %) is in a range from about0.1 to about 0.5 (0.1≤(Li₂O (mol %)/R₂O (mol %)≤0.5), whereR₂O=Li₂O+Na₂O+K₂O+Rb₂O+Cs₂O.

In some embodiments, R₂O (mol %)−Al₂O₃ (mol %) is in a range from about−2 mol % to about 5.6 mol %, where R₂O=Li₂O+Na₂O+K₂O+Rb₂O+Cs₂O. In someembodiments, Al₂O₃ (mol %)>B₂O₃ (mol %). In some embodiments, (Al₂O₃(mol %)+B₂O₃ (mol %))/R₂O (mol %) is in a range from about 0.9 to about1.9. In some embodiments, R₂O (mol %)+R′O (mol %) −Al₂O₃ (mol %) −B₂O₃(mol %)−P₂O₅ (mol %) is in a range from about −10.5 mol % to about −0.11mol %, where R′O=MgO+CaO+SrO+BaO.

In some embodiments, the lithium aluminosilicate glasses describedherein have softening points that are lower than sodium analogs, whichtypically have softening points of greater than about 900° C. In someembodiments, the glasses described herein have softening points of about840° C. or less. In certain embodiments, the glass has a softening pointof about 820° C. or less and, in still other embodiments, about 800° C.or less. These low softening points are accompanied by coefficients ofthermal expansion (CTE) that are lower than those of sodium analogs.Lower CTE is important in maintaining dimensional stability whenreforming glass sheets. In addition to use as flat plates, therelatively low CTEs of the present glasses enable their use asthree-dimensional articles and in automotive applications.

In some embodiments, the lithium aluminosilicate glasses describedherein have an anneal point of at least about 500° C. In certainembodiments the glass has an anneal point of at least about 520° C. and,in still other embodiments, the anneal point is at least about 530° C.

Densities, strain points, softening points, anneal points, andcoefficients of thermal expansion (CTE) for selected glass compositionsare listed in Table 2.

TABLE 2 Compositions, densities, strain points, softening points, annealpoints, and coefficients of thermal expansion (CTE) of selected lithiumaluminosilicate glasses. mol % 196HNT 107UE 107UF 107UG 107UH 107UI SiO₂67.00 67.11 67.18 66.96 67.17 67.20 Al2O₃ 12.60 9.14 10.12 9.13 10.1510.15 B₂O₃ 7.10 0.00 0.00 0.00 0.00 0.00 Li₂O 5.10 8.10 7.66 6.28 5.245.23 Na₂O 6.70 11.38 10.86 13.26 13.27 13.31 K₂O 1.30 0.26 0.27 0.260.26 0.27 MgO 1.17 1.08 1.29 1.12 1.75 CaO 1.82 1.82 1.80 1.78 1.09 SnO₂0.10 0.00 0.00 0.00 0.00 0.00 R₂O—Al₂O₃ 0.50 Li₂O/(R₂O) 0.389 0.4100.408 0.317 0.279 0.278 Strain Pt. (° C.) 459.1 473.2 462.8 482.3 482.3Anneal Pt. (° C.) 500.2 514.1 504.5 525.6 524.9 Softening Pt. (° C.)691.8 719.3 703.8 733 739.7 CTE (×10⁻⁷/° C.) 87.8 84.2 89.9 86.9 87Density (g/cm³) 2.474 2.471 2.479 2.477 2.473 mol % 107UJ 107UK 107UL107UM 107UN 107UO SiO₂ 67.01 70.21 70.17 70.14 71.17 71.19 Al2O₃ 10.148.51 8.50 8.49 7.47 6.88 B₂O₃ 0.00 0.00 0.00 0.00 0.00 0.00 Li₂O 6.305.45 6.49 6.93 5.33 5.28 Na₂O 11.32 11.30 10.32 9.82 11.49 12.09 K₂O0.27 0.98 0.99 0.99 0.99 0.98 MgO 2.15 1.02 0.99 1.06 1.02 1.04 CaO 1.801.53 1.53 1.55 1.53 1.52 SnO₂ 0.00 0.00 0.00 0.00 0.00 0.00 R₂O—Al₂O₃Li₂O/(R₂O) 0.352 0.307 0.365 0.391 0.299 0.288 Strain Pt. (° C.) 485.5469.2 466.8 464.2 460.5 452.8 Anneal Pt. (° C.) 529 511.6 509.5 506.9502.3 495.3 Softening Pt. (° C.) 741 728.6 720.1 714.1 712.3 702.7 CTE(×10⁻⁷/° C.) 83.3 84.2 83.1 82.4 84.5 85.3 Density (g/cm³) 2.474 2.4582.455 2.453 2.454 2.452 mol % 107UP 107UQ 107UR 107US 107UT 107UU SiO₂69.60 66.42 66.49 66.27 66.33 65.31 Al2O₃ 7.78 9.39 9.38 8.09 8.09 6.98B₂O₃ 0.00 0.00 0.00 0.00 0.00 0.00 Li₂O 5.10 6.39 6.37 11.73 10.66 9.65Na₂O 12.90 11.57 11.60 9.98 9.97 10.48 K₂O 0.98 1.23 1.23 0.01 0.01 1.49MgO 1.08 0.05 0.04 0.03 0.04 0.51 CaO 1.55 3.55 2.51 1.05 2.08 2.59 SnO₂0.00 0.00 0.00 0.00 0.00 0.00 R₂O—Al₂O₃ Li₂O/(R₂O) 0.269 0.333 0.3320.540 0.516 0.446 Strain Pt. (° C.) 452.6 474.5 484 460.6 466.7 452.7Anneal Pt. (° C.) 494.2 515.5 526.7 499.5 506.9 492.3 Softening Pt. (°C.) 697 711.3 732.2 693.2 697.6 678.6 CTE (×10⁻⁷/° C.) 90.5 90.1 87.686.7 84.9 92.5 Density (g/cm³) 2.468 2.499 2.519 2.51 2.519 2.539 mol %107UV 107UW 107UX 107UY 107UZ 107VA SiO₂ 65.28 65.86 67.91 69.80 68.0967.98 Al2O₃ 6.96 9.56 8.99 8.49 10.01 10.99 B₂O₃ 0.00 0.00 0.00 0.000.00 0.00 Li₂O 9.67 8.42 7.96 7.40 6.77 5.91 Na₂O 10.49 11.70 10.9410.36 10.96 10.94 K₂O 2.48 0.27 0.27 0.24 0.25 0.27 MgO 0.03 1.09 1.030.98 1.02 1.02 CaO 2.07 1.90 1.79 1.69 1.78 1.78 SnO₂ 0.00 0.11 0.100.09 0.10 0.10 R₂O—Al₂O₃ Li₂O/(R₂O) 0.427 0.413 0.415 0.411 0.376 0.345Strain Pt. (° C.) 448.3 464 464 469 484 503 Anneal Pt. (° C.) 486.2 505506 511 526 548 Softening Pt. (° C.) 671.5 697 706 716 737 772 CTE(×10⁻⁷/° C.) 84.2 90.4 86.7 86.3 83.8 82 Density (g/cm³) 2.537 2.4852.472 2.458 2.47 2.468 mol % 107VB 107VC 107VD 107VE 107VF 107VG SiO₂67.98 67.26 66.04 65.24 66.39 66.15 Al2O₃ 9.00 9.43 9.95 10.46 8.9910.98 B₂O₃ 0.00 0.00 0.00 0.00 0.00 0.00 Li₂O 7.92 7.78 7.82 7.77 7.567.76 Na₂O 10.96 11.39 11.96 12.37 11.94 11.93 K₂O 0.26 0.26 0.27 0.260.26 0.27 MgO 1.34 1.00 1.04 1.01 1.00 1.03 CaO 1.42 1.78 1.82 1.77 1.771.78 SnO₂ 0.10 0.10 0.10 0.10 0.10 0.10 R₂O—Al₂O₃ Li₂O/(R₂O) 0.414 0.4000.390 0.381 0.382 0.389 Strain Pt. (° C.) 466 463 465 468 470 460 AnnealPt. (° C.) 508 505 506 508 512 501 Softening Pt. (° C.) 707 706 702 706712 697 CTE (×10⁻⁷/° C.) 86.3 86.7 89.4 89.4 88.3 89.7 Density (g/cm³)2.469 2.401 2.407 2.432 2.411 2.38 mol % 107VH 107VI 107VJ 107VK 107VL107VM SiO₂ 65.17 65.52 64.53 63.51 62.63 61.19 Al2O₃ 9.96 5.11 6.46 7.719.04 10.39 B₂O₃ 0.00 0.00 0.00 0.00 0.00 0.00 Li₂O 7.73 12.67 11.9511.23 10.52 10.05 Na₂O 11.94 12.40 12.78 13.29 13.59 14.13 K₂O 0.27 0.270.27 0.27 0.26 0.27 MgO 1.78 1.05 1.05 1.04 1.03 1.04 CaO 2.04 1.85 1.831.84 1.80 1.81 SnO₂ 0.10 0.10 0.10 0.10 0.10 0.10 R₂O—Al₂O₃ Li₂O/(R₂O)0.388 0.500 0.478 0.453 0.432 0.411 Strain Pt. (° C.) 465 412 416 426435 443 Anneal Pt. (° C.) 506 447 453 462 471 481 Softening Pt. (° C.)701 602 616 626 640 655 CTE (×10⁻⁷/° C.) 90.1 105.9 104.8 103.5 103.3101.7 Density (g/cm³) 2.413 2.485 2.49 2.495 2.499 2.511 mol % 107VN107VU 107VW 107VX 107VY 107VZ SiO₂ 60.07 68.95 66.00 66.12 68.85 68.81Al2O₃ 11.72 9.97 9.96 9.98 9.96 9.94 B₂O₃ 0.00 0.00 0.00 0.00 0.00 0.00Li₂O 9.21 7.96 5.00 4.99 7.98 9.94 Na₂O 14.75 4.94 7.90 7.90 4.96 2.98K₂O 0.26 0.99 0.99 0.99 0.99 1.01 MgO 1.06 3.57 3.59 3.50 5.10 2.04 CaO1.82 1.54 1.53 1.52 2.05 5.17 SnO₂ 0.10 0.09 0.10 0.09 0.10 0.10R₂O—Al₂O₃ Li₂O/(R₂O) 0.380 0.573 0.360 0.359 0.573 0.714 Strain Pt. (°C.) 452 546.8 524.5 566.4 511.7 500.4 Anneal Pt. (° C.) 492 592.6 570.9611.2 556.4 541.5 Softening Pt. (° C.) 672 825 812.3 830.7 N/A N/A CTE(×10⁻⁷/° C.) 103.1 65.1 74.5 69.4 67.4 66.1 Density (g/cm³) 2.506 2.4782.493 2.531 2.434 2.445 mol % 107WA 107WB 107WC 107WD 107WE 107WF SiO₂68.91 66.92 66.84 68.71 68.63 67.85 Al2O₃ 9.95 9.95 9.95 9.95 8.94 9.95B₂O₃ 0.00 0.00 0.00 0.00 0.00 0.00 Li₂O 6.99 7.94 6.98 7.86 7.82 7.82Na₂O 3.95 4.95 3.95 3.93 4.93 3.97 K₂O 2.94 0.99 2.95 2.95 0.99 2.97 MgO5.10 5.09 5.16 5.44 6.48 6.29 CaO 2.06 2.06 2.08 1.05 2.10 1.05 SnO₂0.10 0.10 0.10 0.10 0.10 0.10 R₂O—Al₂O₃ Li₂O/(R₂O) 0.504 0.572 0.5030.533 0.569 0.530 Strain Pt. (° C.) 513.9 521.2 521.3 503.2 502.8 504.1Anneal Pt. (° C.) 559.4 563.3 564.5 548.8 546.3 548.5 Softening Pt. (°C.) 793.9 770.6 776.6 783.4 766 775.6 CTE (×10⁻⁷/° C.) 70.7 68.6 71.271.1 68 71.7 Density (g/cm³) 2.434 2.465 2.463 2.426 2.436 2.433 mol %107WG 107WH 107WI 107WJ 107WK 107WL SiO₂ 67.70 67.24 67.05 66.54 65.0167.47 Al2O₃ 8.78 8.63 8.46 8.32 7.95 8.57 B₂O₃ 0.00 0.00 0.00 0.00 0.000.00 Li₂O 8.78 9.83 10.69 11.72 12.09 8.34 Na₂O 10.89 10.68 10.46 10.339.87 10.87 K₂O 0.21 0.17 0.11 0.06 0.27 0.72 MgO 0.83 0.64 0.41 0.211.04 1.01 CaO 1.45 1.08 0.72 0.35 1.79 1.63 SnO₂ 0.00 0.00 0.00 0.000.00 0.00 R₂O—Al₂O₃ Li₂O/(R₂O) 0.441 0.475 0.503 0.530 0.544 0.418Strain Pt. (° C.) 458 457 454 457 444 458 Anneal Pt. (° C.) 499 497 496497 483 499 Softening Pt. (° C.) 695 691 689 686 664 693 CTE (×10⁻⁷/°C.) 87.6 88.2 89.7 89.3 92.5 89.4 Density (g/cm³) 2.475 2.482 2.4892.496 2.502 2.479 mol % 107WM 107WN 107WO 107WP 107WQ 107WR SiO₂ 67.1466.58 65.94 66.97 65.95 65.18 Al2O₃ 8.18 7.77 7.40 8.56 8.20 7.83 B₂O₃0.00 0.00 0.00 1.37 2.66 3.92 Li₂O 8.47 8.87 9.27 8.15 8.36 8.54 Na₂O10.76 10.60 10.55 10.52 10.06 9.42 K₂O 1.19 1.63 2.08 0.61 0.93 1.24 MgO1.02 1.04 1.02 1.22 1.40 1.58 CaO 1.46 1.31 1.15 1.41 1.04 0.69 SnO₂0.00 0.00 0.00 0.00 0.00 0.00 R₂O—Al₂O₃ Li₂O/(R₂O) 0.415 0.420 0.4230.423 0.432 0.445 Strain Pt. (° C.) 453 449 448 455 452 454 Anneal Pt.(° C.) 493 490 488 493 491 491 Softening Pt. (° C.) 687 680 679 682 665660 CTE (×10⁻⁷/° C.) 93.6 94 96.1 87.2 87 87.4 Density (g/cm³) 2.4912.505 2.517 2.475 2.48 2.485 mol % 107WS 107WT 107WU 107WV 107WW 107WXSiO₂ 66.97 67.00 67.11 67.13 67.08 67.02 Al2O₃ 9.42 9.45 9.49 9.46 9.499.45 B₂O₃ 0.00 0.00 0.00 0.00 0.00 0.00 Li₂O 5.95 5.91 6.80 5.87 6.855.85 Na₂O 11.40 11.37 11.90 12.38 11.89 12.43 K₂O 0.26 0.27 0.27 0.260.27 0.27 MgO 1.02 3.13 1.55 2.04 1.03 1.04 CaO 3.85 1.78 1.78 1.77 2.292.83 SnO₂ 0.10 0.10 0.10 0.10 0.10 0.10 R₂O—Al₂O₃ Li₂O/(R₂O) 0.338 0.3370.358 0.317 0.360 0.316 Strain Pt. (° C.) 485 485.4 469.7 476.9 469.5477.8 Anneal Pt. (° C.) 527.2 528.6 511.9 518.7 511.7 519.5 SofteningPt. (° C.) 728.3 739.8 715.7 726 712.2 720.8 CTE (×10⁻⁷/° C.) Density(g/cm³) 2.493 2.48 2.479 2.481 2.482 2.488 mol % 107WY 107WZ 107XA 107XB107XC 107XD SiO₂ 68.09 68.08 67.11 66.13 65.19 67.16 Al2O₃ 10.05 10.0610.55 11.04 11.56 11.05 B₂O₃ 0.00 0.00 0.00 0.00 0.00 0.00 Li₂O 7.868.78 7.34 7.83 8.22 7.24 Na₂O 9.85 8.87 10.83 10.83 10.84 10.37 K₂O 0.250.25 0.25 0.25 0.25 0.25 MgO 1.01 1.03 1.03 1.02 1.03 1.03 CaO 1.78 1.811.78 1.79 1.79 1.79 SnO₂ 0.10 0.09 0.10 0.10 0.10 0.10 R₂O—Al₂O₃Li₂O/(R₂O) 0.438 0.490 0.399 0.414 0.426 0.405 Strain Pt. (° C.) 481 479483 483 482 493 Anneal Pt. (° C.) 523 521 526 525 525 536 Softening Pt.(° C.) 736 728 736 731 731 749 CTE (×10⁻⁷/° C.) 83.2 82.2 85.2 84.9 87.381.5 Density (g/cm³) 2.469 2.465 2.476 2.479 2.483 2.473 mol % 107XE107XF 107XG 107XH 107XI 107XJ SiO₂ 65.01 64.58 65.20 65.18 64.25 63.48Al2O₃ 7.26 7.64 6.98 6.97 6.96 6.96 B₂O₃ 0.00 0.00 0.00 0.00 0.00 0.00Li₂O 10.73 11.72 9.80 9.81 9.81 9.69 Na₂O 9.42 8.46 10.41 10.42 10.4210.39 K₂O 2.48 2.50 2.50 2.51 2.46 2.45 MgO 0.03 0.03 0.03 0.03 1.032.02 CaO 2.06 2.06 2.07 2.07 2.05 2.04 SnO₂ 0.00 0.00 0.00 0.00 0.000.00 R₂O—Al₂O₃ Li₂O/(R₂O) 0.474 0.517 0.432 0.431 0.432 0.430 Strain Pt.(° C.) 451.8 451.7 441.9 433.9 446.9 448.8 Anneal Pt. (° C.) 489.7 491.1480 470.6 486.5 487.5 Softening Pt. (° C.) 676.4 676.7 653.5 634 673.5669.7 CTE (×10⁻⁷/° C.) Density (g/cm³) 2.533 2.53 2.511 2.488 2.5432.548 mol % 107XK 107XL 107XM 107XN 107XO 107XP SiO₂ 65.01 64.73 66.6066.58 65.66 65.04 Al2O₃ 7.29 7.69 9.41 9.45 9.42 9.29 B₂O₃ 0.00 0.000.00 0.00 0.00 0.00 Li₂O 10.78 11.68 6.34 6.28 6.34 6.22 Na₂O 9.39 8.4111.50 11.49 11.46 11.45 K₂O 1.47 1.48 1.23 1.23 1.20 1.22 MgO 0.50 0.490.03 0.04 0.98 1.93 CaO 2.56 2.56 2.55 2.54 2.47 2.43 SnO₂ 0.00 0.000.00 0.00 0.00 0.00 R₂O—Al₂O₃ Li₂O/(R₂O) 0.498 0.542 0.332 0.331 0.3340.329 Strain Pt. (° C.) 456.5 457 478.8 470 488.6 489.5 Anneal Pt. (°C.) 494.9 496.4 519.9 509.2 531.2 532.1 Softening Pt. (° C.) 675.4 677714.1 690.4 740 737.8 CTE (×10⁻⁷/° C.) Density (g/cm³) 2.537 2.533 2.4972.548 2.527 2.533 mol % 107XQ 107XR 107XS 107XT 107XU 107XV SiO₂ 67.1666.15 65.20 67.09 66.09 65.07 Al2O₃ 10.07 11.06 12.06 10.06 11.05 12.05B₂O₃ 0.00 0.00 0.00 0.00 0.00 0.00 Li₂O 7.74 7.71 7.70 8.81 9.76 10.73Na₂O 10.88 10.88 10.86 9.87 8.88 7.91 K₂O 0.25 0.25 0.25 0.25 0.25 0.25MgO 0.99 1.03 1.02 1.02 1.04 1.03 CaO 1.79 1.80 1.80 1.78 1.81 1.82 SnO₂0.10 0.10 0.10 0.10 0.10 0.10 R₂O—Al₂O₃ Li₂O/(R₂O) 0.410 0.409 0.4100.465 0.517 0.568 Strain Pt. (° C.) 475 483 494 473 480 490 Anneal Pt.(° C.) 516 525 536 514 522 532 Softening Pt. (° C.) 722 730 748 715 726733 CTE (×10⁻⁷/° C.) 86.5 85.3 86.5 85.1 82.9 81.6 Density (g/cm³) 2.4762.473 2.48 2.483 2.474 2.474 mol % 107XW 107XX 107XY 107XZ 107YA 107YBSiO₂ 64.13 65.70 62.52 57.42 63.87 61.20 Al2O₃ 7.57 7.81 6.98 6.61 4.444.57 B₂O₃ 0.00 0.00 0.00 0.00 0.00 0.00 Li₂O 11.36 9.48 12.12 18.9714.62 17.79 Na₂O 10.92 11.26 11.16 10.73 9.51 9.25 K₂O 0.32 0.22 0.240.21 0.20 0.22 MgO 1.70 1.56 2.21 1.80 2.01 2.03 CaO 2.40 2.28 2.99 2.803.46 3.39 SnO₂ 0.10 0.10 0.10 0.10 0.10 0.10 R₂O—Al₂O₃ Li₂O/(R₂O) 0.5030.452 0.516 0.634 0.601 0.653 Strain Pt. (° C.) 439 450 432 406 420 407Anneal Pt. (° C.) 476 490 469 438 455 441 Softening Pt. (° C.) 645 673629 570 603 581 CTE (×10⁻⁷/° C.) 108.7 104.3 114.1 101.7 95.1 95.9Density (g/cm³) 2.508 2.503 2.524 2.518 2.519 2.515 mol % 107YC 107YD107YE 107YF 107YG 107YH SiO₂ 64.66 65.15 65.25 65.22 65.27 65.26 Al2O₃10.67 11.20 10.68 9.77 10.68 11.19 B₂O₃ 0.00 0.00 0.00 0.00 0.00 0.00Li₂O 8.27 7.96 7.93 8.38 7.91 8.34 Na₂O 11.71 11.22 11.18 11.88 11.2010.73 K₂O 0.27 0.26 0.26 0.28 0.26 0.26 MgO 1.27 1.21 1.21 1.28 1.691.21 CaO 1.95 1.88 1.86 1.98 1.86 1.87 SnO₂ 0.10 0.10 0.10 0.10 0.100.10 R₂O—Al₂O₃ Li₂O/(R₂O) 0.408 0.409 0.409 0.408 0.408 0.432 Strain Pt.(° C.) 471.4 479.4 483.9 462.3 476.3 480.4 Anneal Pt. (° C.) 512.2 521.6526.1 502 518.4 521.8 Softening Pt. (° C.) CTE (×10⁻⁷/° C.) 89.6 87.389.7 90.4 87.6 85.8 Density (g/cm³) 2.491 2.485 2.498 2.49 2.487 2.484mol % 107YL 107YN 107YP 107YQ 107YR 107YS SiO₂ 65.99 66.16 65.12 65.1565.20 65.13 Al2O₃ 9.52 9.54 10.62 10.69 10.69 10.69 B₂O₃ 0.00 0.00 0.000.00 0.00 0.00 Li₂O 6.49 6.49 6.15 9.94 7.89 7.98 Na₂O 11.37 11.38 13.189.25 10.25 9.25 K₂O 1.24 1.23 0.26 0.26 1.25 2.25 MgO 0.26 0.25 1.701.70 1.72 1.70 CaO 2.49 2.51 1.85 1.88 1.87 1.87 SnO₂ 0.09 0.09 0.100.10 0.10 0.10 R₂O—Al₂O₃ Li₂O/(R₂O) 0.340 0.340 0.314 0.511 0.407 0.410Strain Pt. (° C.) 483 473 474 473 Anneal Pt. (° C.) 525 515 517 515Softening Pt. (° C.) 0.314 0.511 0.407 0.410 CTE (×10⁻⁷/° C.) Density(g/cm³) 483 473 474 473 mol % 107YT 107YU 107YV 107AAC 107AAD 107AAESiO₂ 64.10 62.85 65.27 67.60 67.52 67.51 Al2O₃ 10.52 10.33 7.93 8.388.87 9.35 B₂O₃ 1.89 3.70 0.00 0.00 0.00 0.00 Li₂O 7.65 7.56 8.86 8.038.09 8.16 Na₂O 10.96 10.73 10.33 10.72 10.23 9.71 K₂O 0.25 0.24 1.800.95 0.95 0.96 MgO 1.68 1.70 0.18 1.05 1.06 1.04 CaO 1.84 1.80 2.73 1.591.60 1.59 SnO₂ 0.09 0.09 0.09 0.10 0.09 0.10 R₂O—Al₂O₃ Li₂O/(R₂O) 0.4060.408 0.422 0.408 0.420 0.434 Strain Pt. (° C.) 464 466 Anneal Pt. (°C.) 504 503 Softening Pt. (° C.) CTE (×10⁻⁷/° C.) Density (g/cm³) 2.4852.482 2.489 2.487 2.485 mol % 107AAF 107AAG 107AAH 107AAK 107AAL 107AAMSiO₂ 67.45 67.08 67.52 67.73 67.55 67.40 Al2O₃ 8.85 8.87 8.87 8.69 8.638.64 B₂O₃ 0.00 0.00 0.00 0.00 0.00 0.00 Li₂O 8.18 8.06 8.59 9.89 10.0410.20 Na₂O 9.23 10.20 9.71 10.18 10.22 10.22 K₂O 1.96 0.96 0.96 0.310.30 0.30 MgO 1.04 1.55 1.05 0.42 0.43 0.42 CaO 1.60 1.60 1.60 0.72 0.730.73 SnO₂ 0.10 0.09 0.09 0.00 0.00 0.00 R₂O—Al₂O₃ Li₂O/(R₂O) 0.422 0.4190.446 0.485 0.488 0.492 Strain Pt. (° C.) Anneal Pt. (° C.) SofteningPt. (° C.) CTE (×10⁻⁷/° C.) Density (g/cm³) 2.486 2.49 2.485 mol %107AAN 716HZE 716HZJ 716HZQ 716IBA 716IBS SiO₂ 65.67 65.46 65.38 65.4566.14 65.87 Al2O₃ 10.33 9.40 9.39 9.39 10.30 10.33 B₂O₃ 0.00 0.00 0.000.00 0.00 0.00 Li₂O 7.85 6.17 6.13 6.12 7.68 7.71 Na₂O 11.09 11.09 11.1211.01 10.81 11.01 K₂O 0.76 1.16 1.20 1.17 0.71 0.71 MgO 1.39 2.02 1.991.98 1.41 1.42 CaO 1.84 2.40 2.38 2.37 1.81 1.83 SnO₂ 0.00 0.08 0.050.05 0.05 0.03 R₂O—Al₂O₃ Li₂O/(R₂O) 0.398 0.335 0.332 0.334 0.400 0.397Strain Pt. (° C.) 470 483.2 483.1 487.4 466.5 461.2 Anneal Pt. (° C.)512 524.9 526.0 529.3 506.8 502.7 Softening Pt. (° C.) 735.4 742.3 711703.3 CTE (×10⁻⁷/° C.) 87.4 88.7 89.9 89.6 Density (g/cm³) 2.446 2.5322.534 2.485 mol % 716IBT 716IBU 196HLP 196HLQ 196HLR 196HLS SiO₂ 65.9265.96 60.22 60.03 59.88 59.96 Al2O₃ 10.32 10.32 16.94 14.90 16.84 16.85B₂O₃ 0.00 0.00 5.83 5.83 5.95 5.92 Li₂O 7.72 7.72 0.00 0.00 4.98 7.00Na₂O 10.99 10.94 15.85 13.89 11.13 9.07 K₂O 0.70 0.70 1.00 1.00 1.071.06 MgO 1.42 1.41 0.02 4.20 0.01 0.02 CaO 1.81 1.81 0.02 0.05 0.02 0.02SnO₂ 0.03 0.03 0.08 0.08 0.08 0.08 R₂O—Al₂O₃ Li₂O/(R₂O) 0.398 0.3990.290 0.409 Strain Pt. (° C.) 461.6 461.3 578.8 559.1 526.2 520.8 AnnealPt. (° C.) 501.6 502.6 633.6 608.6 577.3 568.4 Softening Pt. (° C.)702.5 703.1 906 858 820 814 CTE (×10⁻⁷/° C.) 89 90.5 89.6 81.7 85.1 78.7Density (g/cm³) 2.406 2.421 2.401 2.395 mol % 196HLT 196HLU 196HQB196HQC 196HQD 196HQE SiO₂ 59.87 59.98 60.432 60.351 60.627 60.462 Al2O₃15.89 14.88 15.212 16.250 16.612 15.760 B₂O₃ 5.88 5.84 5.949 5.951 5.9395.928 Li₂O 6.49 5.98 5.860 5.884 6.080 6.995 Na₂O 8.55 7.94 11.39110.421 9.604 9.665 K₂O 1.05 1.02 0.945 0.935 0.925 0.975 MgO 2.13 4.200.045 0.046 0.046 0.046 CaO 0.03 0.05 0.042 0.042 0.045 0.046 SnO₂ 0.080.08 0.081 0.081 0.081 0.082 R₂O—Al₂O₃ 0.19 0.06 2.98 0.99 0.00 1.87Li₂O/(R₂O) 0.403 0.400 0.322 0.341 0.366 0.397 Strain Pt. (° C.) 509.5511.6 478.6 486.7 499.3 485.8 Anneal Pt. (° C.) 555.7 557.0 519.0 530.1544.9 528.1 Softening Pt. (° C.) 784 784 720 775 815 738 CTE (×10⁻⁷/°C.) 76 71 86.7 82.7 80.9 81.5 Density (g/cm³) 2.406 2.412 2.422 2.4072.398 2.41 mol % 196HQF 196HQG 196HQH 196HQI 196HQJ 196HQK SiO₂ 60.46260.393 60.136 59.979 59.867 60.099 Al2O₃ 14.902 14.918 16.000 16.06614.972 17.064 B₂O₃ 5.948 5.975 6.079 6.026 8.071 4.087 Li₂O 7.350 5.8285.851 5.969 5.724 6.228 Na₂O 9.663 9.985 9.753 11.712 10.175 11.295 K₂O1.450 2.689 1.964 0.028 0.983 0.996 MgO 0.051 0.047 0.045 0.050 0.0410.052 CaO 0.048 0.043 0.045 0.045 0.043 0.048 SnO₂ 0.084 0.083 0.0830.083 0.082 0.083 R₂O—Al₂O₃ 3.56 3.58 1.57 1.64 1.91 1.46 Li₂O/(R₂O)0.398 0.315 0.333 0.337 0.339 0.336 Strain Pt. (° C.) 470.3 471.0 485.5491.9 481.0 500.5 Anneal Pt. (° C.) 510.7 510.9 529.4 536.3 523.6 546.1Softening Pt. (° C.) 701 705 759 756 730 778 CTE (×10⁻⁷/° C.) 85 86.684.1 82.2 82.1 88 Density (g/cm³) 2.42 2.425 2.411 2.413 2.397 2.428 mol% 196HQL 196HQM 196HVQ 196HVR 196HVS 196HVT SiO₂ 60.140 60.048 60.45260.473 60.373 62.560 Al2O₃ 16.090 15.056 16.842 16.335 15.823 15.855B₂O₃ 6.049 6.106 6.039 6.023 6.027 5.918 Li₂O 5.803 5.815 6.683 6.4926.303 6.325 Na₂O 9.716 9.746 8.751 8.474 8.264 8.148 K₂O 0.982 0.9910.995 0.992 0.994 0.973 MgO 1.043 2.053 0.055 1.027 2.029 0.047 CaO0.051 0.059 0.054 0.058 0.061 0.049 SnO₂ 0.082 0.081 0.081 0.079 0.0800.081 R₂O—Al₂O₃ 0.41 1.50 −0.41 −0.38 −0.26 −0.41 Li₂O/(R₂O) 0.352 0.3510.407 0.407 0.405 0.409 Strain Pt. (° C.) 500.8 485.7 Anneal Pt. (° C.)547.1 529.3 Softening Pt. (° C.) 779 746 CTE (×10⁻⁷/° C.) 81 79.3Density (g/cm³) 2.407 2.416 2.395 2.401 2.405 2.385 mol % 196HVU 196HW196HVW 196HVX 196HVY 196HVZ SiO₂ 64.405 62.473 64.869 64.742 64.86059.773 Al2O₃ 14.859 15.816 13.272 13.276 13.287 14.728 B₂O₃ 5.974 5.9735.196 5.165 5.151 5.827 Li₂O 5.825 6.272 4.659 5.790 6.667 5.666 Na₂O7.739 9.220 8.675 7.682 6.689 10.509 K₂O 0.982 0.030 0.026 0.028 0.0310.028 MgO 0.049 0.047 1.509 1.510 1.499 1.970 CaO 0.045 0.049 0.0520.055 0.058 0.058 SnO₂ 0.080 0.079 0.006 0.009 0.008 0.005 R₂O—Al₂O₃−0.31 −0.29 0.09 0.22 0.10 −0.31 Li₂O/(R₂O) 0.400 0.404 0.349 0.4290.498 0.400 Strain Pt. (° C.) Anneal Pt. (° C.) Softening Pt. (° C.) CTE(×10⁻⁷/° C.) Density (g/cm³) 2.375 2.386 2.408 2.406 2.403 2.375 mol %196HVZ 196HWA 196HWB 196HXW 196HXX 196HXY SiO₂ 59.773 59.271 58.89060.00 60.00 60.00 Al2O₃ 14.728 14.635 14.544 16.75 16.25 15.75 B₂O₃5.827 5.826 5.797 6.00 6.00 6.00 Li₂O 5.666 5.626 5.587 6.25 6.00 5.75Na₂O 10.509 10.436 10.325 10.00 9.75 9.50 K₂O 0.028 0.028 0.028 1.001.00 1.00 MgO 1.970 1.988 1.960 0.00 1.00 2.00 CaO 0.058 0.061 0.061SnO₂ 0.005 0.005 0.005 0.08 0.08 0.08 R₂O—Al₂O₃ 1.47 1.46 1.40 0.50 0.500.50 Li₂O/(R₂O) 0.350 0.350 0.351 0.362 0.358 0.354 Strain Pt. (° C.)496 Anneal Pt. (° C.) 541 Softening Pt. (° C.) 796 CTE (×10⁻⁷/° C.) 81.1Density (g/cm³) 2.435 2.446 2.458 2.401 mol % 196HXZ 196HYA 196HYB SiO₂60.00 60.00 62.00 Al2O₃ 16.25 16.75 16.75 B₂O₃ 6.00 6.00 4.00 Li₂O 5.506.50 6.25 Na₂O 9.25 10.75 10.00 K₂O 1.00 0.00 1.00 MgO 2.00 0.00 0.00CaO SnO₂ 0.08 0.08 0.08 R₂O—Al₂O₃ −0.50 0.50 0.50 Li₂O/(R₂O) 0.349 0.3770.362 Strain Pt. (° C.) Anneal Pt. (° C.) Softening Pt. (° C.) CTE(×10⁻⁷/° C.) Density (g/cm³) 2.435 2.446 2.458

The lithium aluminosilicate glasses described herein, in someembodiments, may have an elastic modulus of at least about 68gigaPascals (GPa).

In addition to exemplary compositions of lithium silicate glasses,physical properties, including strain, anneal, and softening points;CTE; and density of these example glasses are listed in Table 2. Thestrain point was determined using the beam bending viscosity method ofASTM C598-93(2013). The annealing point was determined using the beambending viscosity method of ASTM C598-93(2013). The softening point wasdetermined using the parallel plate viscosity method of ASTMC1351M-96(2012). The linear coefficient of thermal expansion (CTE) overthe temperature range 0-300° C. is expressed in terms of ppm/K and wasdetermined using a push-rod dilatometer in accordance with ASTM E228-11.The density was determined using the buoyancy method of ASTMC693-93(2013).

In some embodiments, the lithium aluminosilicate glasses describedherein have a liquidus viscosity of greater than about 10,000 Poise (P)and, in certain embodiments, greater than 100,000 P. In someembodiments, these glasses are compatible with fusion processes, such asfusion draw processes or the like, and compatible with zircon hardwareused in forming. However, in some embodiments (e.g., example 3 inTable 1) these glasses have low liquidus viscosities and are thereforenot fusion-formable. In these instances, the glass may be formed by slotdraw, float, rolling, and other sheet-forming processes known in theart.

The glasses described herein may be formed into articles such as, butnot limited to, flat plates and three dimensional articles havingthicknesses ranging from about 0.2 mm up to about 2 mm and, in someembodiments, from about 0.5 mm to about 1.5 mm.

The viscosity and mechanical performance are influenced by glasscompositions. In the glass compositions described herein, SiO₂ serves asthe primary glass-forming oxide and can serve to stabilize thenetworking structure. The concentration of SiO₂ should be sufficientlyhigh in order to provide the glass with sufficiently high chemicaldurability suitable for consumer applications. However, the meltingtemperature (200 poise temperature) of pure SiO₂ or high content SiO₂glasses is too high to allow the glass to be processed by certainmethods. Furthermore, the presence of SiO₂ decreases the compressivestress created by ion exchange. In some embodiments, the lithiumaluminosilicate glasses described herein comprise from about 55 mol % toabout 75 mol % SiO₂, such as from about 57 mol % to about 73 mol % SiO₂;from about 59 mol % to about 71 mol % SiO₂; from about 61 mol % to about69 mol % SiO₂; from about 63 mol % to about 67 mol % SiO₂; from about 55mol % to about 60 mol % SiO₂; from about 58 mol % to about 69 mol %SiO₂; or any sub-ranges contained therein.

Al₂O₃ may also serve as a glass former in these glasses. Like SiO₂,alumina generally increases the viscosity of the melt, and an increasein Al₂O₃ relative to the alkalis or alkaline earths generally results inimproved durability. The structural role of the aluminum ions depends onthe glass composition. When the concentration of alkali metal oxides(R₂O) is close to or greater than the concentration of alumina (Al₂O₃),all aluminum is found in tetrahedral coordination with the alkali metalions acting as charge-balancers. This is the case for all of the glassesdescribed herein. In general, Al₂O₃ also plays an important role in ionexchangeable glasses, as it enables a strong network backbone (i.e.,high strain point) while allowing for the relatively fast diffusivity ofalkali ions. However, high Al₂O₃ concentrations generally lower theliquidus viscosity and thus Al₂O₃ concentration needs to be controlledin a reasonable range. In some embodiments, the glasses described hereincomprise from about 9 mol % to about 18 mol % Al₂O₃, such as from about10 mol % to about 18 mol % Al₂O₃; from about 12 mol % to about 16 mol %Al₂O₃; from about 12 mol % to about 15 mol % Al₂O₃; from about 9 mol %to about 17 mol % Al₂O₃; or any sub-ranges contained therein.

Alkali oxides (Li₂O, Na₂O, K₂O, Rb₂O, and Cs₂O) serve as aids inachieving low melting temperature and low liquidus temperatures. On theother hand, the addition of alkali oxide dramatically increases thecoefficient of thermal expansion (CTE) and lowers the chemicaldurability. Most importantly, to perform ion exchange, the presence ofat least one small alkali oxide such as Li₂O and Na₂O is required toexchange with larger alkali ions (e.g., K⁺) from an ion exchange medium,such as a salt bath. Three types of ion exchange can generally becarried out: Na⁺-for-Li⁺ exchange, which results in a deep depth oflayer but low compressive stress; K⁺-for-Li⁺ exchange, which results ina small depth of layer but a relatively large compressive stress; andK⁺-for-Na⁺ exchange, which results in intermediate depth of layer andcompressive stress. Because compressive stress is proportional to thenumber of alkali ions that are exchanged out of the glass, asufficiently high concentration of the at least one small alkali oxideis needed to produce a large compressive stress in the glass. In someembodiments, the glasses described herein comprise from about 2.5 mol %to about 20 mol % Li₂O, such as from about 3 mol % to about 20 mol %Li₂O; from about 4 mol % to about 18 mol % Li₂O; from about 5 mol % toabout 16 mol % Li₂O; from about 6 mol % to about 14 mol % Li₂O; fromabout 5 mol % to about 14 mol % Li₂O; from about 7 mol % to about 10 mol% Li₂O; from about 2.5 mol % to about 12 mol % Li₂O; from about 4 mol %to about 10 mol % Li₂O; or any sub-ranges contained therein. In someembodiments, these glasses comprise from 0 mol % to about 14 mol % Na₂O;such as from 0 mol % to about 5 mol % Na₂O; from about 0.2 mol % toabout 12 mol % Na₂O; from about 4 mol % to about 14 mol % Na₂O; from 0.2mol % to about 14 mol % Na₂O; or any sub-ranges contained therein. Theglasses described herein, in some embodiments, may comprise from 0 mol %to about 4 mol % K₂O, such as from 0 mol % to about 2.5 mol % K₂O; from0 mol % to about 1 mol % K₂O; or any sub-ranges contained therein.

To achieve a high liquidus viscosity and thus make formation bydown-draw techniques, particularly by the fusion draw method, Li₂O glassshould account for less than half of the total alkali oxide content on amolar basis. When Li₂O/(Li₂O+Na₂O+K₂O+Rb₂O+Cs₂O) exceeds 0.5, thespodumene liquidus increases and the glasses are no longer compatiblewith the fusion technique. Thus, in some embodiments,Li₂O/(Li₂O+Na₂O+K₂O+Rb₂O+Cs₂O) is in a range from about 0.1 to about0.5; such as 0.1≤Li₂O/(Li₂O+Na₂O+K₂O+Rb₂O+Cs₂O)≤0.4,0.2≤Li₂O/(Li₂O+Na₂O+K₂O+Rb₂O+Cs₂O)≤0.4, or any sub-ranges containedtherein. To achieve high compressive stress at depth after ion exchange,however, it is desirable to maximize the Li₂O content. To achieve acompressive stress of greater than 100 MPa at depths greater than 40 um,the Li₂O content should therefore be greater than about 4 mol % and, insome embodiments, preferably greater than about 5 mol %, and should beless than about 10 mole %.

The presence of K₂O increases the rate of K⁺ for Na⁺ ion exchange butdrastically decreases the compressive stress after ion exchange. In someembodiments, the glass should comprise less than about 2.5 mol % K₂Oand, in certain embodiments, the K₂O concentration should not exceed 1mole %.

Divalent cation oxides (such as alkaline earth oxides and zinc oxide)also improve the melting behavior of the glass. With respect to ionexchange performance, however, the presence of divalent cations acts todecrease alkali cation mobility. This negative effect on ion exchangeperformance is especially pronounced with the larger divalent cations.Furthermore, the smaller divalent cation oxides generally help enhancethe compressive stress more than the larger divalent cation oxides.Hence, MgO offers several advantages with respect to improved stressrelaxation while minimizing the adverse effects on alkali diffusivity.However, when the contents of MgO are high, the glasses are prone toform forsterite (Mg₂SiO₄), which causes the liquidus temperature to risevery steeply as MgO concentration rises above a certain level. In someembodiments, MgO is the only divalent cation oxide present in the glass.In other embodiments, the glasses described herein may contain at leastone of MgO and ZnO. Accordingly, these glasses, in some embodiments, maycomprise from 0 mol % to about 8 mol % MgO, such as from 0 mol % toabout 6 mol % MgO; from 0 mol % to about 5 mol % MgO; from 0 mol % toabout 3 mol % MgO; from 0 mol % to about 1 mol % MgO; or any sub-rangescontained therein. In some embodiments, the glass may comprise from 0mol % to about 4 mol % ZnO, such as from 0 mol % to about 3 mol % ZnO;from 0 mol % to about 2 mol % ZnO; from 0 mol % to about 1 mol % ZnO, orany sub-ranges contained therein.

When boron is not charge balanced by alkali oxides or divalent cationoxides, it will be in a trigonal coordination state, and thus open upthe glass structure. The network around the trigonally coordinated boronis not as rigid as those surrounding tetrahedrally coordinated boron;the bonds are “floppy (i.e. elastic, flexible, or capable of bending orstretching)” and therefore allow the glasses to tolerate somedeformation before crack formation. Furthermore, boron decreases themelting viscosity and effectively helps suppress the zircon breakdownviscosity of the glass. In some embodiments, the glasses describedherein contain from 0 mol % to about 20 mol % B₂O₃, such as from about2.5 mol % to about 20 mol % B₂O₃; from about 3 mol % to about 18 mol %B₂O₃; from about 3.5 mol % to about 16 mol % B₂O₃; from about 4 mol % toabout 16 mol % B₂O₃; from about 4.5 mol % to about 14 mol % B₂O₃; fromabout 5 mol % to about 12 mol % B₂O₃; from about 2.5 mol % to about 7.5mol % B₂O₃; from about 5 mol % to about 7 mol % B₂O₃; from about 3.5 mol% to about 9.5 mol % B₂O₃; from about 5 mol % to about 9 mol % B₂O₃; orany sub-ranges contained therein.

P₂O₅ improves damage resistance and does not impede ion exchange. Insome embodiments, the addition of phosphorous to the glass creates astructure in which silica (SiO₂ in the glass) is replaced by aluminumphosphate (AlPO₄), which consists of tetrahedrally coordinated aluminumand phosphorus and/or boron phosphate (BPO₄), which consists oftetrahedrally coordinated boron and phosphorus. In some embodiments, theglass comprises from 0 to about 4 mol % P₂O₅, such as from 0 mol % toabout 3 mol % P₂O₅; from 0 mol % to about 2.5 mol % P₂O₅; from 0 mol %to about 1 mol % P₂O₅; or any sub-ranges contained therein.

TiO₂ serves as a nucleation agent to produce bulk nucleation if aglass-ceramic article is desired. If the concentration of TiO₂ is toolow, the precursor glass does not crystallize. If the concentration istoo high, the devitrification, upon cooling during precursor glassforming, can be difficult to control. In some embodiments, the glassesdescribed herein may comprise from 0 mol % to about 5 mol % TiO₂, suchas from 0 mol % to about 4 mol % TiO₂; from 0 mol % to about 3 mol %TiO₂; from 0 mol % to about 2 mol % TiO₂; from 0 mol % to about 1 mol %TiO₂; or any sub-ranges contained therein.

In some embodiments, the glasses described herein may further include atleast one fining agent such as, but not limited to, SnO₂, As₂O₃, Sb₂O₃,and the like. Due to environmental and toxicity concerns, As₂O₃ andSb₂O₃ are typically not included in glasses. Accordingly, the glassesdescribed herein are typically free of As₂O₃ and Sb₂O₃ and, in someembodiments, these glasses may comprise from about 0.05 mol % to about0.5 mol % SnO₂.

Rare earth oxides may increase the hardness and elastic modulus of aglass, but they hamper ion exchange, increase the density and cost ofthe glass, and many impart color to the glass. It is therefore desirableto limit the total rare earth oxide content to less than 0.1 mol %.

In some aspects, the lithium aluminosilicate glasses described hereinare strengthened by forming a compressive layer on the surfaces of theglass. In certain embodiments, these glasses are chemicallystrengthened, and in particular embodiments, are chemically strengthenedby ion exchange.

Ion exchange is a process in which smaller cations in the glass areexchanged for larger cations that are present in an ion exchange mediumsuch as a molten salt bath or a paste. In a particular embodiment, ionexchange is carried out by immersing the glass in a molten salt bathsubstantially comprising a salt of the larger cation. The ion exchangebath may also comprise salts of the smaller cations that are present inthe glass. As used herein, the term “substantially comprising” meansthat other components may be present in the molten salt bath. Suchcomponents may include, but are not limited to, compounds that act toreduce attack of the bath vessel or the glass article by the moltensalt. Such additional components may include, but are not limited to,selected components of the glass, such as silicic acid, alumina in gelform, silica in gel form, or the like.

A cross-sectional schematic view of an ion exchanged glass article isshown in FIG. 1 . Glass article 100 has a thickness t, first surface110, and second surface 112. Glass article 100, in some embodiments, hasa thickness t of up to about 1 mm. While the embodiment shown in FIG. 1depicts glass article 100 as a flat planar sheet or plate, glass articlemay have other configurations, such as three dimensional shapes ornon-planar configurations. Glass article 100 has a first compressivelayer 120 extending from first surface 110 to a depth of layer (DOL) d₁into the bulk of the glass article 100. In the embodiment shown in FIG.1 , glass article 100 also has a second compressive layer 122 extendingfrom second surface 112 to a second depth of layer d₂. First and secondcompressive layers 120, 122 are each under a compressive stress CS. Insome embodiments, first and second compressive layers 120, 122 each havea maximum compressive stress at the first and second surfaces 110, 112,respectively. Glass article also has a central region 130 that extendsfrom d₁ to d₂. Central region 130 is under a tensile stress or centraltension (CT), which balances or counteracts the compressive stresses oflayers 120 and 122. The depths of layer d₁, d₂ of first and secondcompressive layers 120, 122 protects the glass article 100 from thepropagation of flaws introduced by sharp impact to first and secondsurfaces 110, 112 of glass article 100, while the compressive stress ofat least about 900 MPa minimizes the likelihood of a flaw penetratingthrough the depth d₁, d₂ of first and second compressive layers 120,122.

When ion exchanged, the lithium aluminosilicate glasses described hereintypically exhibit, relative to their sodium analogs, deep depths oflayer and low central tension, thus enabling very thin (i.e., <0.5 mm)sheets of glass to be chemically strengthened while not beingsusceptible to frangible behavior.

Compressive stress (including surface CS) is measured by surface stressmeter (FSM) using commercially available instruments such as theFSM-6000, manufactured by Orihara Industrial Co., Ltd. (Japan). Surfacestress measurements rely upon the accurate measurement of the stressoptical coefficient (SOC), which is related to the birefringence of theglass. SOC in turn is measured according to Procedure C (Glass DiscMethod) described in ASTM standard C770-16, entitled “Standard TestMethod for Measurement of Glass Stress-Optical Coefficient,” thecontents of which are incorporated herein by reference in theirentirety.

As used herein, DOL means the depth at which the stress in thechemically strengthened alkali aluminosilicate glass article describedherein changes from compressive to tensile. DOL may be measured by FSMor a scattered light polariscope (SCALP) depending on the ion exchangetreatment. Where the stress in the glass article is generated byexchanging potassium ions into the glass article, FSM is used to measureDOL. Where the stress is generated by exchanging sodium ions into theglass article, SCALP is used to measure DOL. Where the stress in theglass article is generated by exchanging both potassium and sodium ionsinto the glass, the DOL is measured by SCALP, since it is believed theexchange depth of Na⁺ ions (“Potassium DOL”) indicates the DOL and theexchange depth of potassium ions indicates a change in the magnitude ofthe compressive stress (but not the change in stress from compressive totensile). The depth of penetration of K+ ions (“Potassium DOL”)represents the depth of potassium penetration as a result of an ionexchange process. The Potassium DOL is typically less than the DOL forthe articles described herein. Potassium DOL is measured using a surfacestress meter such as the commercially available FSM-6000 surface stressmeter, manufactured by Luceo Co., Ltd. (Tokyo, Japan), which relies onaccurate measurement of the stress optical coefficient (SOC), asdescribed above with reference to the CS measurement.

The lithium aluminosilicate glasses described herein may be subjected toan ion exchange process in at least one molten salt bath containingeither sodium salts, potassium salts, or both sodium and potassiumsalts. The nitrate salts NaNO₃ and KNO₃ are typically used in the ionexchange process. The glasses are held in a salt bath for a timesufficient for ion exchange to occur on the surface and into some depthinto the article. In one embodiment, the glass is chemicallystrengthened by immersion in a molten salt bath comprising NaNO₃ for apredetermined time period to achieve a desired level of ion exchange. Asa result of the ion exchange, a surface compressive layer is createdcaused by the substitution of Li⁺ ions contained in a glass surfacelayer by Na⁺ or K⁺ ions, both of which have a larger ionic radius thanLi⁺. In one embodiment, the temperature of the molten salt bath is about390° C. and the predetermined time period is in a range from about oneto four hours. In other embodiments, ion exchange is carried out in atleast one molten salt bath at temperatures ranging from about 370° C. toabout 390° C.

In some embodiments, the glasses described herein may undergo ionexchange with monovalent silver cations, thus providing the glasssurface with antimicrobial properties. Since the ionic radius of Ag⁺ isgreater than that of either Li⁺ or Na⁺, silver ion exchange of theseglasses results in a lower loss of compressive stress than observed inion exchanged glasses that contain only sodium and potassium.

In some embodiments, the lithium aluminosilicate glasses describedherein may be ion exchanged to achieve a depth of layer of at leastabout 70 μm when ion exchanged for periods of less than about 7 hours.In addition, these glasses may be ion exchanged to achieve maximumcompressive stresses at the surface of the glass of at least about 500MPa in a one-step ion exchange process, or at least about 600 MPa in atwo-step ion exchange process, with some glasses achieving maximumcompressive stresses as high as 840 MPa in a one-step ion exchange andas high as 1000 MPa at the glass surface in a two-step ion exchangeprocess. In some embodiments, a compressive stress of at least 700 MPa,or at least about 800 MPa, or at least about 900 MPa may be achievedusing either a one-step or a two-step ion exchange process. In someembodiments, the compressive stress in these ion exchanged glasses maybe about 50 MPa or greater at depths of 100 μm or more below thesurface.

The lithium aluminosilicate glasses described herein may be ionexchanged to achieve depths of compressive layer of at least about 70μm; in some embodiment, at least about 100 μm; and in still otherembodiment, at least about 150 μm by either one-step or two-step ionexchange processes. The ion exchange time at temperatures ranging 370°C. to about 390° C. needed to achieve these depths of layer by either aone-step or two-step process is less than about 7 hours.

The profile and depth of the compressive layer may be determined fromthe concentration profile of the larger cations participating in the ionexchange process. The Na⁺ concentration profile from the surface of theglass to the inner portion of a 1) lithium aluminosilicate glass(example 3 in Table 1) and a glass ceramic (Corning Code 9667; nominalcomposition listed in Table 1) that had been cerammed at 975° C. for 4hours) that were ion exchanged at 390° C. for 3.5 hours in a NaNO₃molten salt bath are shown in FIG. 2 . In some embodiments, a depth oflayer DOL of at least 100 μm, determined from the Na₂O concentrationprofile, may be achieved for the lithium aluminosilicate glass (1 inFIG. 2 ).

Table 3 lists conditions for one-step ion exchange, CS, depth of K⁺penetration into the glass, and depth of Na⁺ penetration into the glassfor compositions selected from Table 2. Two-step ion exchangeconditions, fictive temperature T^(f), CS, and DOL for compositionsselected from Table 2 are listed in Table 4.

TABLE 3 One-step ion exchange conditions, compressive stress (CS), andK⁺ and Na⁺ penetration for compositions selected from Table 2. 196HLP196HLQ 196HLR 196HLS 196HLT 196HLU Ion exchange in 100 wt % KNO₃ at 430°C. for 2 hours CS (MPa) 998 861 876 860 905 881 K⁺ DOL (μm) 40 25 22 1914 11 Ion exchange in 90 wt % KNO₃/10 wt % NaNO₃ at 390° C. for 3 hoursCS (MPa) 637 581 683 701 728 667 K⁺ DOL (μm) 29.6 17.5 13.6 10.1 8.2 7.5Na⁺ DOL (μm) 244 267 237 247 Ion exchange in 80 wt % KNO₃/20 wt % NaNO₃at 390° C. for 3 hours CS (MPa) 512 460 606 658 633 651 K⁺ DOL (μm) 29.016.3 13.5 9.8 7.3 7.9 Na⁺ DOL (μm) 280 273 237 224 Ion exchange in 60 wt% KNO₃/40 wt % NaNO₃ at 390° C. for 3 hours CS (MPa) 348 302 505 542 K⁺DOL (μm) 26.9 15.7 12.6 8.7 Na⁺ DOL (μm) 244 293 198 195 Ion exchange in100 wt % NaNO₃ at 370° C. for 0.75 hour CS (MPa) Na⁺ DOL (μm) 198 182185 192 196HQB 196HQC 196HQD 196HQE 196HQF 196HQG Ion exchange in 95 wt% KNO_(3/5) wt % NaNO₃ at 390° C. for 3 hours CS (MPa) 722 780 822 779721 651 K⁺ DOL (μm) 8.3 9.8 10.7 7.9 7.1 10.4 Na⁺ DOL (μm) 215 221 228202 215 182 Ion exchange in 90 wt % KNO₃/10 wt % NaNO₃ at 390° C. for 3hours CS (MPa) 670 693 741 695 695 582 K⁺ DOL (μm) 7.8 9.9 10.1 7.4 6.910.9 Na⁺ DOL (μm) 224 228 250 224 234 195 Ion exchange in 80 wt %KNO₃/20 wt % NaNO₃ at 390° C. for 3 hours CS (MPa) 568 604 639 599 579486 K⁺ DOL (μm) 7.6 9.8 10.0 7.5 7.1 8.9 Na⁺ DOL (μm) 202 241 208 244231 205 Ion exchange in 100 wt % NaNO₃ at 370° C. for 0.75 hour CS (MPa)Na⁺ DOL (μm) 189 192 179 176 182 182 196HQH 196HQI 196HQJ 196HQK 196HQL196HQM Ion exchange in 95 wt % KNO_(3/5) wt % NaNO₃ at 390° C. for 3hours CS (MPa) 713 789 707 848 822 766 K⁺ DOL (μm) 11.2 7.7 9.9 10.2 8.87.0 Na⁺ DOL (μm) 182 241 202 250 228 224 Ion exchange in 80 wt % KNO₃/20wt % NaNO₃ at 390° C. for 3 hours CS (MPa) 539 629 613 652 611 602 K⁺DOL (μm) 10.5 5.4 5.3 9.1 8.1 7.2 Na⁺ DOL (μm) 192 254 202 257 234 195Ion exchange in 60 wt % KNO₃/40 wt % NaNO₃ at 390° C. for 3 hours CS(MPa) 455 503 460 528 510 485 K⁺ DOL (μm) 9.6 7.4 8.1 8.8 8.3 7.6 Na⁺DOL (μm) 205 260 185 244 237 205 Ion exchange in 100 wt % NaNO₃ at 370°C. for 0.75 hour CS (MPa) Na⁺ DOL (μm) 172 169 169 169 172 172

TABLE 4 Two-step ion exchange conditions, fictive temperature T_(f), CS,and DOL for compositions selected from Table 2. 196HLR 196HLS 196HLT196HLU T_(f) (° C.) 652 638 623 623 Bath 1 Temperature (° C.) 390 390390 390 Time (hr) 0.75 0.75 0.75 0.75 Composition (wt %) 80% 80% 80% 80%KNO₃ KNO₃ KNO₃ KNO₃ 20% 20% 20% 20% NaNO₃ NaNO₃ NaNO₃ NaNO₃ Bath 2Temperature (° C.) 390 390 390 390 Time (hr) 0.75 0.75 0.75 0.75Composition (wt %) 100% 100% 100% 100% KNO₃ KNO₃ KNO₃ KNO₃ CS (MPa) 10411068 1042 DOL (μm) 185 195 163 195

Vickers crack initiation thresholds described herein are determined byapplying and then removing an indentation load to the glass surface at arate of 0.2 mm/min. The maximum indentation load is held for 10 seconds.The indentation cracking threshold is defined at the indentation load atwhich 50% of 10 indents exhibit any number of radial/median cracksemanating from the corners of the indent impression. The maximum load isincreased until the threshold is met for a given glass composition. Allindentation measurements are performed at room temperature in 50%relative humidity. The test involved the use of a square-based pyramidaldiamond indenter with an angle of 136° between faces, referred to as aVickers indenter. The Vickers indenter was same as the one used instandard micro hardness testing (reference ASTM-E384-11).

As used herein, the term “Knoop Scratch Threshold” refers to the onsetof lateral cracking. In Knoop threshold testing, a mechanical testerholds a Knoop diamond in which a glass is scratched at increasing loadsto determine the onset of lateral cracking. As used herein, KnoopScratch Threshold is the onset of lateral cracking (in 3 or more of 5indentation events). In Knoop Scratch Lateral Cracking Thresholdtesting, samples of the glass articles and articles were first scratchedwith a Knoop indenter under a dynamic or ramped load to identify thelateral crack onset load range for the sample population. Once theapplicable load range is identified, a series of increasing constantload scratches (3 minimum or more per load) are performed to identifythe Knoop scratch threshold. The Knoop scratch threshold range can bedetermined by comparing the test specimen to one of the following 3failure modes: 1) sustained lateral surface cracks that are more thantwo times the width of the groove, 2) damage is contained within thegroove, but there are lateral surface cracks that are less than twotimes the width of groove and there is damage visible by naked eye, or3) the presence of large subsurface lateral cracks which are greaterthan two times the width of groove and/or there is a median crack at thevertex of the scratch.

When ion exchanged in NaNO₃, the glasses described herein exhibit highnative damage resistance, and, in some embodiments, capable of achievinga Vickers crack initiation threshold of over 50 kilogram force (kgf).This level of damage resistance may be achieved, for example, for theglasses described herein containing 6 mol % Li₂O following ion exchangeat 390° C. in a NaNO₃ bath for 3.5 hours. This Vickers crack initiationthreshold value is comparable to—or greater than—those exhibited byanalogous sodium aluminosilicate glasses having high levels of inherentdamage resistance. FIG. 3 is a plot of indentation fracture thresholds(IFT) determined after ion exchange in KNO₃ for the present lithiumaluminosilicate glass (example 3 in Table 1, ion exchanged at 390° C. inNaNO₃ for 3.5 hours) (C in FIG. 3 ), and in fusion-formed sodiumaluminosilicate glasses A and E (nominal composition: 67.6 mol % SiO₂;3.7 mol % B₂O₃; 12.7 mol % Al₂O₃; 13.7 mol % Na₂O; 0.01 mol % K₂O; 2.3mol % MgO; and 0.1 mol % SnO₂) with IFT of 15-20 kgf; glass B (nominalcomposition: 64.7 mol % SiO₂; 5.1 mol % B₂O₃; 13.9 mol % Al₂O₃; 13.7 mol% Na₂O; 2.4 mol % MgO; and 0.08 mol % SnO₂) with IFT of 30-40 kgf; andglass D (nominal composition: 64.7 mol % SiO₂; 5.1 mol % B₂O₃; 13.9 mol% Al₂O₃; 13.7 mol % Na₂O; 2.4 mol % MgO; and 0.08 mol % SnO₂) with IFTof 15 kgf Optical microscopic images of Vickers indentations in the ionexchanged lithium aluminosilicate glass plotted in FIG. 3 under indenterloads of 10 kgf (a in FIG. 4 ), 30 kgf (b), and 50 kgf (c) are shown inFIG. 4 . The images in FIG. 4 show significant glass densificationwithout formation of lateral cracking, indicating that the glasspossesses a high level of inherent damage resistance.

In some embodiments, the glasses described herein, when ion exchanged asdetailed above, may exhibit Vickers crack initiation thresholds (VIT) ofat least 10 kgf; in some embodiments, at least 15 kgf; and in stillother embodiments, at least about 20 kgf. In certain embodiments, theVickers crack initiation threshold is in a range from about 10 kgf toabout 35 kgf and Knoop scratch thresholds (KST) are in a range fromabout 10 Newtons (N) to about 20 N.

Vickers crack initiation thresholds (VIT) and Knoop scratch thresholds(KST) for glasses that were ion exchanged in one-step and two-step ionexchange processes are listed in Tables 3 and 4, respectively.

The articles disclosed herein may be incorporated into another articlesuch as an article with a display (or display articles) (e.g., consumerelectronics, including mobile phones, tablets, computers, navigationsystems, and the like), architectural articles, transportation articles(e.g., automotive, trains, aircraft, sea craft, etc.), appliancearticles, or any article that requires some transparency,scratch-resistance, abrasion resistance or a combination thereof. Anexemplary article incorporating any of the strengthened articlesdisclosed herein is shown in FIGS. 5A and 5B. Specifically, FIGS. 5A and5B show a consumer electronic device 200 including a housing 202 havingfront 204, back 206, and side surfaces 208; electrical components (notshown) that are at least partially inside or entirely within the housingand including at least a controller, a memory, and a display 210 at oradjacent to the front surface of the housing; and a cover substrate 212at or over the front surface of the housing such that it is over thedisplay. In some embodiments, the cover substrate 212 and/or housing mayinclude any of the strengthened articles disclosed herein.

While typical embodiments have been set forth for the purpose ofillustration, the foregoing description should not be deemed to be alimitation on the scope of the disclosure or appended claims.Accordingly, various modifications, adaptations, and alternatives mayoccur to one skilled in the art without departing from the spirit andscope of the present disclosure and appended claims.

The invention claimed is:
 1. A lithium aluminosilicate glass article,wherein the lithium aluminosilicate glass article is formed from a glasscomprising: from 55 mol % to 75 mol % SiO₂; from 10 mol % to 18 mol %Al₂O₃; and from 5 mol % to 14 mol % Li₂O, wherein Li₂O (mol %)/R₂O (mol%) is in a range from 0.15 to 0.4, R₂O=Li₂O+Na₂O+K₂O+Rb₂O+Cs₂O, and thelithium aluminosilicate glass article is ion exchanged and has acompressive layer extending to a depth of layer of at least 70 μm fromat least one surface into the lithium aluminosilicate glass article, thecompressive layer having a maximum compressive stress of at least 600MPa, wherein the lithium aluminosilicate glass article has a Vickerscrack initiation threshold of at least 10 kgf and a Knoop scratchthreshold of at least 8 N.
 2. The lithium aluminosilicate glass articleof claim 1, wherein the glass from which the lithium aluminosilicateglass article is formed comprises from 0 mol % to 20 mol % B₂O₃.
 3. Thelithium aluminosilicate glass article of claim 1, wherein the glass fromwhich the lithium aluminosilicate glass article is formed comprises from0 mol % to 5 mol % Na₂O.
 4. The lithium aluminosilicate glass article ofclaim 1, wherein the glass from which the lithium aluminosilicate glassarticle is formed comprises from 0 mol % to 4 mol % K₂O.
 5. The lithiumaluminosilicate glass article of claim 1, wherein the glass from whichthe lithium aluminosilicate glass article is formed comprises from 0 mol% to 8 mol % MgO.
 6. The lithium aluminosilicate glass article of claim1, wherein the glass from which the lithium aluminosilicate glassarticle is formed comprises from 0 mol % to 4 mol % ZnO.
 7. The lithiumaluminosilicate glass article of claim 1, wherein the glass from whichthe lithium aluminosilicate glass article is formed comprises from 0 mol% to 5 mol % TiO₂.
 8. The lithium aluminosilicate glass article of claim1, wherein the glass from which the lithium aluminosilicate glassarticle is formed comprises from 0 mol % to 4 mol % P₂O₅.
 9. The lithiumaluminosilicate glass article of claim 1, wherein the glass from whichthe lithium aluminosilicate glass article is formed comprises from 0.05mol % to 0.5 mol % SnO₂.
 10. The lithium aluminosilicate glass articleof claim 1, the glass from which the lithium aluminosilicate glassarticle is formed comprises: from 55 mol % to 60 mol % SiO₂; from 12 mol% to 15 mol % Al₂O₃; from 2.5 mol % to 7.5 mol % B₂O₃; from 7 mol % to10 mol % Li₂O; and from 0 mol % to 3 mol % P₂O₅.
 11. The lithiumaluminosilicate glass article of claim 1, wherein the glass from whichthe lithium aluminosilicate glass article is formed is characterized byAl₂O₃ (mol %)>B₂O₃ (mol %).
 12. The lithium aluminosilicate glassarticle of claim 1, wherein the glass from which the lithiumaluminosilicate glass article is formed is characterized by R₂O (mol%)−Al₂O₃ (mol %) is in a range from −2 mol % to 5.6 mol %.
 13. Thelithium aluminosilicate glass article of claim 1, wherein the glass fromwhich the lithium aluminosilicate glass article is formed ischaracterized by R₂O (mol %)+R′O (mol %) −Al₂O₃ (mol %) −B₂O₃ (mol %)−P₂O₅ (mol %) is in a range from −10.5 mol % to −0.11 mol %, whereR′O=MgO+CaO+SrO+BaO.
 14. The lithium aluminosilicate glass article ofclaim 1, wherein the glass from which the lithium aluminosilicate glassarticle is formed is characterized by (Al₂O₃ (mol %)+B₂O₃ (mol %))/R₂O(mol %) is in a range from 0.9 to 1.9.
 15. The lithium aluminosilicateglass article of claim 1, wherein the glass from which the lithiumaluminosilicate glass article is formed has an anneal point of at least510° C.
 16. The lithium aluminosilicate glass article of claim 1,wherein the lithium aluminosilicate glass article has a softening pointof 840° C. or less.
 17. The lithium aluminosilicate glass article ofclaim 1, wherein the glass from which the lithium aluminosilicate glassarticle is formed has a liquidus viscosity of at least 10 kP.
 18. Thelithium aluminosilicate glass article of claim 1, wherein the glass fromwhich the lithium aluminosilicate glass article is formed has an elasticmodulus of at least 68 GPa.
 19. The lithium aluminosilicate glassarticle of claim 1, wherein the compressive layer has a compressivestress of at least 100 MPa at a depth of 50 μm below the at least onesurface.
 20. A consumer electronic product, comprising: a housing havinga front surface, a back surface and side surfaces; electrical componentsprovided at least partially within the housing, the electricalcomponents including at least a controller, a memory, and a display, thedisplay being provided at or adjacent the front surface of the housing;and a cover glass disposed over the display, wherein at least one of aportion of the housing or the cover glass comprises the lithiumaluminosilicate glass article of claim 1.